feat: Allow opening a single-file diff from file history view (#6599)

This PR adds a small icon link to the file history list to open the diff for *only* this file in the respective commit. This is very useful if the commit in question touches a very large amount of files and finding the actual file in the diff is tedious.

- fixes #6596

Co-authored-by: Gusted <postmaster@gusted.xyz>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6599
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Yann Büchau <nobodyinperson@posteo.de>
Co-committed-by: Yann Büchau <nobodyinperson@posteo.de>

options/locale/locale_en-US.ini

@@ -1453,6 +1453,7 @@ commits.signed_by_untrusted_user_unmatched = Signed by untrusted user who does n
 commits.gpg_key_id = GPG key ID
 commits.ssh_key_fingerprint = SSH key fingerprint
 commits.view_path=View at this point in history
+commits.view_single_diff = View changes to this file introduced in this commit
 
 commit.operations = Operations
 commit.revert = Revert

templates/repo/commits_list.tmpl

@@ -81,6 +81,14 @@
 						<td class="text right aligned tw-py-0">
 							<button class="btn interact-bg tw-p-2" data-tooltip-content="{{ctx.Locale.Tr "copy_hash"}}" data-clipboard-text="{{.ID}}">{{svg "octicon-copy"}}</button>
 							{{if not $.PageIsWiki}}
+							{{if $.FileName}}
+							<a
+								class="btn interact-bg tw-p-2"
+								data-tooltip-content="{{ctx.Locale.Tr "repo.commits.view_single_diff"}}"
+								href="{{printf "%s/commit/%s?files=%s" $commitRepoLink (PathEscape .ID.String) (PathEscapeSegments $.FileName)}}">
+								{{svg "octicon-file-diff"}}
+							</a>
+							{{end}}
 							<a
 								class="btn interact-bg tw-p-2"
 								data-tooltip-content="{{ctx.Locale.Tr "repo.commits.view_path"}}"

tests/integration/view_test.go

@@ -131,7 +131,7 @@ func TestAmbiguousCharacterDetection(t *testing.T) {
 	})
 }
 
-func TestInHistoryButton(t *testing.T) {
+func TestCommitListActions(t *testing.T) {
 	onGiteaRun(t, func(t *testing.T, u *url.URL) {
 		user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
 		session := loginUser(t, user2.Name)
@@ -164,6 +164,7 @@ func TestInHistoryButton(t *testing.T) {
 			htmlDoc.AssertElement(t, fmt.Sprintf(".commit-list a[href^='/%s/src/commit/']", repo.FullName()), false)
 		})
 
+		fileDiffSelector := fmt.Sprintf(".commit-list a[href='/%s/commit/%s?files=test.sh']", repo.FullName(), commitID)
 		t.Run("Commit list", func(t *testing.T) {
 			defer tests.PrintCurrentTest(t)()
 
@@ -172,6 +173,7 @@ func TestInHistoryButton(t *testing.T) {
 			htmlDoc := NewHTMLParser(t, resp.Body)
 
 			htmlDoc.AssertElement(t, fmt.Sprintf(".commit-list a[href='/%s/src/commit/%s']", repo.FullName(), commitID), true)
+			htmlDoc.AssertElement(t, fileDiffSelector, false)
 		})
 
 		t.Run("File history", func(t *testing.T) {
@@ -182,6 +184,7 @@ func TestInHistoryButton(t *testing.T) {
 			htmlDoc := NewHTMLParser(t, resp.Body)
 
 			htmlDoc.AssertElement(t, fmt.Sprintf(".commit-list a[href='/%s/src/commit/%s/test.sh']", repo.FullName(), commitID), true)
+			htmlDoc.AssertElement(t, fileDiffSelector, true)
 		})
 	})
 }